Revert "drm/i915/dmabuf: fix broken build"

This reverts commit 777226da ("drm/i915/dmabuf: fix broken build").

Approach taken in the patch was rejected by Linus and the upstream tree
now already contains the required include directive via 304ac803
("Merge tag 'drm-next-2021-11-12' of git://anongit.freedesktop.org/drm/drm").
Signed-off-by: Tvrtko Ursulin <tvrtko.ursulin@intel.com>
Fixes: 777226da ("drm/i915/dmabuf: fix broken build")
Cc: Matthew Auld <matthew.auld@intel.com>
Cc: Thomas Hellström <thomas.hellstrom@linux.intel.com>
Cc: Daniel Vetter <daniel.vetter@ffwll.ch>
Cc: Joonas Lahtinen <joonas.lahtinen@linux.intel.com>
Cc: Rodrigo Vivi <rodrigo.vivi@intel.com>
Cc: Jani Nikula <jani.nikula@intel.com>
Acked-by: Matthew Auld <matthew.auld@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20211122135758.85444-1-tvrtko.ursulin@linux.intel.com
[tursulin: fixup commit message sha format]

drivers/gpu/drm/i915/gem/i915_gem_dmabuf.c

@@ -17,13 +17,6 @@
 
 MODULE_IMPORT_NS(DMA_BUF);
 
-#if defined(CONFIG_X86)
-#include <asm/smp.h>
-#else
-#define wbinvd_on_all_cpus() \
-	pr_warn(DRIVER_NAME ": Missing cache flush in %s\n", __func__)
-#endif
-
 I915_SELFTEST_DECLARE(static bool force_different_devices;)
 
 static struct drm_i915_gem_object *dma_buf_to_obj(struct dma_buf *buf)